hash_tables.h

// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.// Use of this source code is governed by a BSD-style license that can be// found in the LICENSE file.////// Deal with the differences between Microsoft and GNU implemenations// of hash_map. Allows all platforms to use |base::hash_map| and// |base::hash_set|.// eg:// base::hash_map<int> my_map;// base::hash_set<int> my_set;//// NOTE: It is an explicit non-goal of this class to provide a generic hash// function for pointers. If you want to hash a pointers to a particular class,// please define the template specialization elsewhere (for example, in its// header file) and keep it specific to just pointers to that class. This is// because identity hashes are not desirable for all types that might show up// in containers as pointers.#ifndef BASE_HASH_TABLES_H_#define BASE_HASH_TABLES_H_#include "build/build_config.h"#include "base/string16.h"#if defined(COMPILER_MSVC)#include <hash_map>#include <hash_set>namespace base {
using stdext::hash_map;
using stdext::hash_set;
}
#elif defined(COMPILER_GCC)// This is a hack to disable the gcc 4.4 warning about hash_map and hash_set// being deprecated. We can get rid of this when we upgrade to VS2008 and we// can use <tr1/unordered_map> and <tr1/unordered_set>.#ifdef __DEPRECATED#define CHROME_OLD__DEPRECATED __DEPRECATED#undef __DEPRECATED#endif#include <ext/hash_map>#include <ext/hash_set>#include <string>#ifdef CHROME_OLD__DEPRECATED#define __DEPRECATED CHROME_OLD__DEPRECATED#undef CHROME_OLD__DEPRECATED#endifnamespace base {
using __gnu_cxx::hash_map;
using __gnu_cxx::hash_set;
} // namespace basenamespace __gnu_cxx {
// The GNU C++ library provides identiy hash functions for many integral types,// but not for |long long|. This hash function will truncate if |size_t| is// narrower than |long long|. This is probably good enough for what we will// use it for.#define DEFINE_TRIVIAL_HASH(integral_type) \ template<> \ struct hash<integral_type> { \ std::size_t operator()(integral_type value) const { \ return static_cast<std::size_t>(value); \ } \ }
DEFINE_TRIVIAL_HASH(longlong);
DEFINE_TRIVIAL_HASH(unsignedlonglong);
#undef DEFINE_TRIVIAL_HASH// Implement string hash functions so that strings of various flavors can// be used as keys in STL maps and sets. The hash algorithm comes from the// GNU C++ library, in <tr1/functional>. It is duplicated here because GCC// versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI// is disabled, as it is in our build.#define DEFINE_STRING_HASH(string_type) \ template<> \ struct hash<string_type> { \ std::size_t operator()(const string_type& s) const { \ std::size_t result = 0; \ for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \ result = (result * 131) + *i; \ return result; \ } \ }
DEFINE_STRING_HASH(std::string);
DEFINE_STRING_HASH(std::wstring);
#if defined(WCHAR_T_IS_UTF32)// If string16 and std::wstring are not the same type, provide a// specialization for string16.
DEFINE_STRING_HASH(string16);
#endif // WCHAR_T_IS_UTF32#undef DEFINE_STRING_HASH
} // namespace __gnu_cxx#endif // COMPILER#endif // BASE_HASH_TABLES_H_